Electronic systems and circuits have made a significant contribution towards the advancement of modem society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems have facilitated increased productivity and reduced costs in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. Frequently, these advantageous results are realized through the use of information stored on a memory media and manipulated by a processing device. The type of memory storage medium can have significant impacts on the performance of an information processing system.
Numerous electronic devices include processors that operate by executing software comprising a series of instructions for manipulating data in the performance of useful tasks. The instructions and associated data are typically stored in a memory. Memories usually consist of a location for storing information and a unique indicator or address. The utility a device provides often depends upon the speed and efficiency at which instructions are executed. The ability to access a memory and transfer information quickly and conveniently usually has a significant impact on information processing latency. The configuration of a memory usually affects the speed at which memory locations are accessed.
Certain types of memories built upon flash memory technologies usually offer the potential for relatively fast information access. Flash memories typically include flash memory cells arranged in a matrix in which each cell is characterized by a voltage operating range. A charge level in a floating gate of the flash memory cell controls whether or not a flash memory cell turns “on” or “off” when a threshold voltage level within the operating range is applied to a gate of the flash memory cell.
Flash memory arrays usually offer a number of desirable characteristics. Flash memories are usually nonvolatile and can retain information even if power is turned off. Flash memory cells are able to store a charge in the floating gate even though system power is turned off and thereby maintain an indication of whether a logical 1 or logical 0 value is “stored” in the cell. Flash memories typically allow random access to data and in-system programmability similar to dynamic random access memory (DRAM). Flash memories are typically solid state and able to withstand shock vibrations and environmental conditions better than electromechanical devices such as a hard drive.
While flash memories offer a variety of potential advantageous characteristics, utilizing traditional flash memories often gives rise to some potential problems. While flash memories may have relatively fast read operations, they traditionally also have relatively long programming times. It often takes in the order of milliseconds to reach the desired level of charge in a floating gate. In addition, flash memories are typically susceptible to over erasing in which an excessive charge condition is established in the floating gate. A corrective programming operation is typically used to correct over-erasing. The relationship between the threshold voltage and the charge correction operation is basically exponential making it difficult to control. During traditional charge correction operations to correct over erasing conditions the threshold voltage levels keep rising as the corrective programming time increases. The continued increase in threshold voltage level often causes an over programming issue. Traditional attempts at correcting over-erasing are often difficult to implement and add significant additional time to programming operations. In addition, traditional attempts at achieving greater flash cell concentration by using short channels with high drain induced barrier loading (DIBL) often cause many problems during corrective programming such as high leakage current. Additional resulting strains on voltage pumps often reduce drain voltage levels and further increasing corrective programming difficulties and reduction of cells that can be serviced by the voltage pump.
An efficient flash memory system and method is desirable.